ILLINI's explanation matches my own experience as a baseball umpire (kids through mens amateur).
The initial sign was a downward slash of the right hand, which indicates "bounced pitch", followed by a short pumped fist motion which is "Strike Three" (not Ball four...which was the other possibility on that particular pitch).
Angels catcher blew the play, plain and simple. Sucks to put it on him, but he's the one who "tossed" the game away with his careless response.
Every catcher is trained to ALWAYS tag the runner if there's ANY doubt.
The ump may have misread the bounce, but his actions following were consistent with a decision that's what he saw.
He didn't reverse anything.